For various reasons, the use of high voltage capacitors with internal winding fuses is increasing. These high voltage capacitors are made up of "building blocks" or banks of capacitors and fuses. In these high voltage capacitors, it is impossible to determine faulty banks by visible inspection of the internal fuses. It is therefore important to ascertain the faulty state of the capacitor banks by electrical measurements. The equipment presently on the market is not satisfactory since it requires very time-consuming measurements of all the capacitors so that possible faults can be recognized. There is thus a need for a simple device by which a fault can be located with a reduction in the number of measurements needed to a fraction of the present number of required measurements.